Definition
An in-line vibrometer is an instrument system used to continuously monitor mechanical vibration parameters. It collects vibration signals in real time through fixed-mounted sensors and converts the data into readable information for evaluating the operating status of the equipment. Unlike portable vibration detection equipment, online vibration meters enable continuous monitoring of critical equipment and are an important part of predictive maintenance and condition monitoring systems.
Principle
The working principle of the online vibrometer is based on vibration sensing and signal processing technology. The system usually consists of vibration sensors, signal conditioning modules, data acquisition units, and analysis software. Vibration sensors, such as piezoelectric accelerometers, convert mechanical vibrations into electrical signals that are proportional to them. After amplification, filtering, and other conditioning, the signal is converted to analog by the data acquisition unit. Finally, the digital signal is analyzed through the built-in algorithm, and the characteristic parameters such as amplitude and frequency of vibration are calculated. Its core measurement relationship can be expressed by the following formula:
a(t) = (d²x)/(dt²)
where a(t) is the instantaneous acceleration and x is the displacement. By integrating the acceleration signal, the vibration velocity and displacement information can also be obtained.
Measurement method
The in-line vibration measurement mainly adopts the direct contact measurement method. The sensor is rigidly installed at the equipment monitoring point through threads or magnetic bases, and usually chooses a position that can reflect the overall vibration state such as the bearing housing and housing. The measurement parameters mainly include vibration displacement, vibration velocity and vibration acceleration. For rotating machinery, the effective value of vibration velocity is generally used as an index to evaluate the steady-state operating state. For shock or high-frequency vibration analysis, acceleration parameters are often used. The system can be set to continuous or triggered acquisition modes and supports real-time spectrum analysis to identify specific fault frequency components.
Influencing factors
The measurement accuracy of an online vibrometer is influenced by several factors. The quality of the sensor installation is the key, and improper flatness, cleanliness and installation torque of the mounting surface will lead to measurement errors. Changes in ambient temperature can affect sensor sensitivity and electronic component performance. Electromagnetic interference can cause noise to analog signals in transmission. The surface condition of the object being measured, the material, and the way the sensor cable is secured can also introduce interference. In addition, whether the frequency response range and range of the system itself match the vibration characteristics of the measured are directly affected.
Applications
Online vibrometers are widely used in industrial fields where operational stability is required. In the power industry, it is used to monitor the bearing condition of steam turbines, generators, fans and water pumps. In the petrochemical field, compressors, centrifugal pumps, and large reactor agitators are continuously monitored. In the metallurgical industry, the operating conditions of rolling mills and crushers are monitored. In the cement manufacturing industry, it is used for condition monitoring of critical fans and large motors. In the water sector, unit vibrations at water pumping stations are monitored. Its core value lies in the early identification of potential problems such as equipment imbalances, misalignments, bearing wear or gear engagement failures through trend analysis, which provides a basis for planned repairs.
Selection considerations
The selection of an online vibration measurement system needs to be comprehensively considered. First, it is necessary to clarify the monitoring objectives, and determine the physical quantities (acceleration, velocity, or displacement) that need to be monitored and the desired frequency response range based on the equipment type, speed range, and common failure modes. Secondly, assess environmental conditions, including temperature, humidity, and the presence of explosive or corrosive media, which determine the level of protection and material requirements of the sensor and housing. Thirdly, consider system integration needs, such as output signal type, communication interface protocol, compatibility with existing control systems. Installation feasibility, such as sensor size, mounting method, and space constraints, should also be evaluated. Finally, it is necessary to consider the scalability of the system, whether it supports increasing the number of channels, and whether the functions of the data analysis software meet the diagnostic needs.